We need to see a test. Also, it may be that this drive is not more efficient than other drives in development.
The Emdrive is "electrically powered". To produce this electrical energy efficiently, we must use a fuel cell or solar panels. As a physics student, an educated guess tells me solar panels will not provide enough energy to make a quick transit toward the outer-planets. Thus, the main energy supply should come from a fuel cell.
If this drive works, one need simple compare efficiencies with an ion thruster, for example.